Flanking

If you are making a Melee Attack against an opponent and you have an ally on the other side of an opponent so that the opponent is directly between the two of you, you are Flanking that opponent. You gain a +2 Flanking bonus on your Melee Attack Roll. See the diagrams below for examples of Flanking.

You don't gain a Flanking bonus when making a Ranged Attack.

AnakinSkywalker and Obi-Wan Kenobi are Flanking the Super Battle Droid. They each gain a +2 Flanking bonus on Melee Attacks against the Droid.

Ki-Adi-Mundi and Agen Kolar are Flanking the Dwarf Spider Droid. They each gain a +2 Flanking bonus on Melee Attacks against the Droid.